With the increasing use of various modern aggressive medical cares, the incidence of serious invasive fungal infections, particularly those caused by Candida spp. and Aspergillus spp., has continued to increase in immuno- logically or physiologically compromised patients [1–3]. However, antifungal agents approved for the treatment of invasive fungal infections are limited in number and clinical usefulness, and fungal isolates resistant to the avail- able drugs have become more prevalent [4,5]. Therefore, the development of new antifungal agents with increased clinical usefulness in terms of efficacy and/or safety is needed.